Re: Return-to-idle tuning
Posted: Tue Apr 07, 2020 9:00 pm
In theory but I've already got the throttle stop open to absolute max now, under some conditions it will completely close the IAC and still idle a touch above target. However many other times it needs more steps just before moving to closed loop idle, especially if stomping on the brakes. PCV is also a factor here as its a controlled leak, changing to an adjustable valve that allows fine-tuning to suit the cam helped give a bit more control.
Its not a matter of the IAC not reacting in time, no changes are commanded unless its in closed loop idle or one of the transition situations as discussed above applies (but often none do, or its hard to strike a balance as above). Even with the delay for closed loop idle set to 0 it still takes a moment for the stop to register (is there a way to set a max road speed for idle?) and the change to occur, plenty of time for it to drop to very low rpm if not stall. It doesn't take much to drive around this but with a good EFI system it'd be nice to tune it out completely.
Not sure how people with actual big cams (like 260+ @0.050) get on with this? I guess they are all running 1200rpm idle with high stall autos.
Its not a matter of the IAC not reacting in time, no changes are commanded unless its in closed loop idle or one of the transition situations as discussed above applies (but often none do, or its hard to strike a balance as above). Even with the delay for closed loop idle set to 0 it still takes a moment for the stop to register (is there a way to set a max road speed for idle?) and the change to occur, plenty of time for it to drop to very low rpm if not stall. It doesn't take much to drive around this but with a good EFI system it'd be nice to tune it out completely.
Not sure how people with actual big cams (like 260+ @0.050) get on with this? I guess they are all running 1200rpm idle with high stall autos.